(Mode of Action of Drugs)

PharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamics

Chapter

1.4

Chapter

2.3

Narcotic Analgesics

(Opioids)(Opioids)(Opioids)(Opioids)(Opioids)

Narcotic Analgesics

Analgesics are the drugs (natural or syn-
thetic origin) which relieve pain by acting
on CNS or peripheral pain mechanism
without causing loss of consciousness.
Dental pain is the initial sign of any den-
tal disease which is usually acute in
nature. In dentistry, non-steroidal anti-
inflammator drugs (NSAID’s) are
commonly employed for dental pain and
inflammation which may be due to caries,
abscess tooth extraction or after any den-
tal procedures. Analgesics can be divided
into two main groups:

a. Opioid/narcotic/morphine like an-
algesics.
b. Nonopioid/nonnarcotic/aspirin
like analgesics.
Drugs obtained from morphine are
known as opioids or narcotic analgesics.

The opium is obtained from the opium
poppy Papaver somniferum. It contains two
type of alkaloids e.g. phenanthrene deriva-
tives (morphine, codeine & thebaine) and
benzyl isoquinoline derivatives (papaverine
and noscapine).

The opioid analgesics are classified as
in table 2.3.1.

NATURAL COMPOUNDS

MORPHINE

Opium is the milky exudate obtained by

incising the unripe seed capsule of the

poppy plant Papaver somniferum and mor-

phine is the most important alkaloid of

opium. Morphine produces analgesia

through action in the brain and spinal

cord, that contain peptides possessing

opioid like pharmacological action. These

endogenous substances are known as

endogenous opioid peptides (earlier

known as endorphin & now known as

βββββ-endorphin).

Morphine and other opioids exert their

pharmacological actions by acting on dif-

ferent receptors namely mu (μ), kappa (κκκκκ)

and delta (δδδδδ).

Analgesic, respiratory, depression as

well as euphoria produced by morphine

result mainly from action at mu recep-

tors. Most of the currently available nar-

cotic analgesics act primarily on the mu

receptors.